Spinal cord injury (SCl) is a devastating condition currently affecting approximately 200,000 people in the United States, with approximately 10,000 new cases diagnosed each year 4'5. Following injury to the spinal cord, endogenous progenitor cells are activated and participate in a partial restoration of the injury zone 6'7'8. The anatomical source of dividing progenitor cells following spinal cord lesion is now a major focus of study. Here we propose that new spinal cord gila are generated from separate astrocyte and oligodendrocyte producing aNPC lineages. We hypothesize that epidermal growth factor (EGF) specifically directs the formation of the oligodendrocyte lineage from activated progenitor cells following traumatic spinal cord injury. This hypothesis is based on the following observations. First, acute mitotic labeling in the adult spinal cord reveals only two significant populations of dividing cells: astrocyte and oligodendrocyte progenitor cells. Second, EGF infused intraventricularly selectively increases the proliferation of oligodendrocyte progenitor cells but not astrocyte progenitor cells. Thirdly, fate determination of EGF expanded progenitor cells shows an increase in new oligodendrocytes but no change in the number of new astrocytes. We propose to use a combination of molecular and histological tools to determine if EGF can selectively amplify glial progenitor cells in a model of SCI. Aim I will determine the effect of EGF on proliferation of progenitor cells and net survival of differentiated gila in a model of spinal cord trauma. Aim II will characterize the fate of a distinct population of glial progenitor cells that respond to EGF. Aim III will characterize the formation of myelin by EGF expanded progenitor cells following injury. These studies will lead to a better understanding of the molecular controls that govern stem cell fate following injury and potentially reveal a novel mechanism for inducing cellular regeneration.